The IP multimedia subsystem (IMS) is a new type of network through which multimedia communications can be established between users and between users and applications. In the IMS network, session initiation protocol or SIP is the signaling protocol used to establish communication sessions. The entities involved in establishing a communication session in an IMS network include call session control functions (CSCFs) that communicate with each other using the SIP protocol.
One problem with the conventional call setup scenarios in an IMS network occurs when a terminating SIP server or call session control function becomes unavailable. When an originating SIP server or call session control function receives a request to establish a communication, the originating SIP server may attempt to contact a terminating SIP server. If the terminating SIP server is unavailable, the originating SIP server may be required to wait for a timeout period defined by SIP call processing before attempting to contact an alternate server. The originating SIP server typically does not store state information for terminating SIP servers. As a result, when a second communication setup request arrives at the originating SIP server, the originating SIP server may again attempt to contact the failed terminating SIP server. Repeated attempts to contact a failed terminating SIP server and the associated time out periods waste resources of the originating SIP server and delay call establishment.
Accordingly, in light of these difficulties, there exists a need for methods, systems, and computer program products for inhibiting message traffic to an unavailable terminating SIP server.